johson rev loss

[fadgy]

I have a johnson/ suzuki (same engine) 60 hp 4 stroke outboard year 2005
For some reason it developed a problem with attaining and maintaining its revs.
When it starts up it idles perfectly but moving off will only build up to 3500 revs yet if i turn off the engine and turn it back on immediately and open the throttle it will quickly build to 5100/ 5200. It will maintain this rev level for approx 1 to 2 minutes before dropping down to 3500 revs.I bought this engine from new and it has only recently developed this problem.The marine engineer/dealer for johnson has spent 5 out of the last 8 days working on this problem without finding the solutionThe Iac valve ,The fuel vapor separator ,The powerpack, the spark plugs, the fuel filter, the high pressure fuel pump, the low pressure fuel pump have all been changed.He has even tried a different fuel tank and fuel line.
There is not a fitting or part on this motor that has not been changed and all checked with the laptop and diagnostic software for this engine. No alarms are sounding or faults being recorded , all sensors are working and yet still the problem persists. I would really appreciate any ideas or other peoples experiences in regard to this type of problem as it is totally baffling not only myself but also the engineer, who i should add i have used for the last 12 years and is very good at what he does. any input please

 

[HighTrim]

Re: johson rev loss

Im no expert, but sounds like SLOW is being activated, Verify the engine is not actually over-heating by using a digital pyrometer.Check the routing of the tan temperature wires. The tan wires have to be located as far away as possible from the spark plug wires.

 

[HighTrim]

Re: johson rev loss

Other things to check:

1. If the engine runs fine until you get above 4900 RPM and then starts missing, check the Orange to Orange/Black power coil wires with an oscilloscope (If available) or replace the pack. A breakdown inside the pack could cause RFI noise to activate the rev limiter for no apparent reason.
2. Using the Piercing Probes and DVA adapter, check the DVA voltage at the RPM where the problem is occurring while connected as follows:

Red Lead: Black Lead: DVA
Brown :Brown/Yellow: 150V +

NOTE: The readings should rapidly increase as the engine RPM increases and stabilize below 400 volts (voltage exceeding 400 V DVA indicates a bad pack). A sharp drop in voltage right before the miss becomes apparent usually indicates a bad stator charge coil.

3. Connect an inductive tachometer to the spark plug wires one at a time and compare the readings. If most of the cylinders show the same reading and one or two show different readings, check the primary wires with the inductive pickup to see if the readings are the same coming out of the power pack. A difference in readings between the primary and secondary coil wires usually indicate a bad coil or bad ignition wires. No difference indicates a bad power pack.

Using the Piercing Probes and DVA adapter, check the DVA voltage while connected as follows:

Red Lead: Black Lead : DVA
Orange :Orange/Black: 11-24V

NOTE: The readings should rapidly increase as the engine RPM increases and stabilize below 24 volts (voltage exceeding 24 V DVA indicates a bad pack). A sharp drop in voltage right before the miss becomes apparent usually indicates a bad stator winding. A sharp drop in voltage when you let off of the starter solenoid indicates a bad power coil on the stator.

 

[fadgy]

Re: johson rev loss

Thanks for the input High Trim but engineer given up after spending 10 days on the problem (his estimation not mine), basically left me hanging with an engine just over 2 years old, that i bought from his company, from new at a cost of just under ?5,000, that wont reach its revs. guess i was asking too much to expect him to actually find and fix the problem , even though i was paying for it.

 

[tashasdaddy]

Re: johson rev loss

the 4 stroke is new technology for a lot of the long time outboard mechs. contact the BRP johnson/evinrude Regional manager. i don't have a clue to your problem. if it was a 2 stroke i would look at carboration.

 

[HighTrim]

Re: johson rev loss

Im not a mechanic, nor an engineer, but he seems to be leaning towards a fuel delivery problem , judging by the parts lists he has changed, which is I feel is not where your problem lies. But thats just my 2 cents. Have you definately verified that it is not going into SLOW? Are the temp wires routed away from the plug wires? The other tests supplied generally end in changing the PP, which you already have, the stator charge coil, the ignition coil or wires, or a bad power coil on the stator. Try replacing these, and if he lets you return the parts that dont help out, you may find your problem. At the very least check them out again. Good luck.

 

[fadgy]

Re: johson rev loss

Just to let you know, engineer found the problem with my motor. 2 of the injectors were playing up. solved the probs with one of them by taking out filter but had to change other one. The ECM on the motor was trying to compensate for the problem by altering setting for iac valve etc.
Took him 6 weeks to get there, tried all sorts of replacement parts including 2 new fuel pumps, 1 new iac valve and changing ignition coils but found it in the end.
For anyone who may have similair problems in the future with this type of motor, get the engineer to run an actuator test on their laptop ( suzuki or johnson dealers have the diagnostic software) its a 2 minute process which will show up any problems with the injectors, and save you going through the nightmare i had.
Many Thanks to all for their input and ideas.